Purpose:
To investigate the effects of visible light on human corneal epithelial cells and the impact of natural antioxidants on oxidative stress produced by light overexposure.

Methods:
Light emitting diode with various wavelengths (410-830nm) was used to irradiate on human corneal epithelial cells, and then cell viability was assessed. Production of reactive oxygen species (ROS) was analyzed using the 2’,7’-dichlorodihydrofluorescein diacetate (DCF-DA). Ethyl alcohol (EtOH) extracts were prepared from the mixture of various medicinal plants. After application of the EtOH extracts, free-radical-scavenging activity was measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The induction of antioxidant enzymes including heme oxygenase-1 (HO-1), peroxireoxin-1 (Prx-1), catalase (CAT), and superoxide dismutase-2 (SOD-2) and inhibitory capability of ROS by the extracts were evaluated by real time-PCR and DCF-DA in human corneal epithelial cells.

Results:
The viability of human corneal epithelial cells was diminished after irradiation of blue light (above 10J at 410nm and 50J at 480nm). ROS production by blue light irradiation increased in a dose dependant manner. EtOH extracts had potent radical scavenging activity. The application of the extracts increased the expression of HO-1, Prx-1 , CAT, and SOD-2 and attenuated ROS production by blue light.